The present invention relates to a biological filtration system for removing ammonia and nitrite from a water supply. More particularly, the present invention relates to a biological filtration system which improves the efficiency of the nitrification process of water passing through the filtration system.
Although the preferred embodiment of the present invention is disclosed with regard to filtering a water supply in a closed system such as an aquarium, it is understood that the present invention can be used for filtering other water supplies. In particular, by scaling of the sizes of the components of the biological filtration system of the present invention, the filtration system may be used to filter a municipal water supply or a water supply drawn from a well or reservoir.
Ammonia (NH.sub.3) or (NH.sub.3).sup.+4 depending upon the pH of water is a chemical compound that is very toxic. In a closed water supply system with a finite amount of water, such as in an aquarium, the ammonia level in the water can build up to toxic levels very rapidly. Ammonia builds up in the water supply from two sources. A first source of ammonia is animals which consume plant protein. This plant protein is broken down and excreted as urea, uric acid, or ammonia. Both urea and uric acid are quickly converted by bacteria into ammonia. A second source of ammonia is the break down of proteins and other nitrogen containing organic compounds by heterotrophic bacteria in a process called mineralization. Ammonia is a nonorganic compound which results from mineralization.
High levels of ammonia deplete oxygen through process of diffusion. Biological filtration is used to combat the problem of ammonia build up in the closed environment of an aquarium. Biological filtration is a process by which bacteria oxidize ammonia into a less toxic form. Oxidation of ammonia occurs in a two step process. In the first step, ammonia is oxidized by nitrifying bacteria in the genus Nitrosomonas or other related genera into nitrite (NO.sub.2). Nitrite is less harmful than ammonia but can still be dangerous in quantities greater than one part per million. Nitrite is further oxidized by nitrifying bacteria in the genus Nitrobacter or other related genera to form nitrate (NO.sub.3). Nitrate is diluted from closed system through periodic water changes.
Various types of biological filters are known. Wet/dry filtration systems work by running water over a vast surface area, usually a tray containing biomedia with water dripping over it. Nitrifying bacteria grow on the surface area of the biomedia. These filtration systems therefore provide a large surface area for nitrifying bacteria to grow and greater water surface coverage for the exchange of gases.
One known biological filter is a trickle filter. In a conventional trickle filter, water passes through a trickle section of the filter and takes on dissolved gases by diffusion. Water draining from the aquarium is coarsely prefiltered to keep out large chunks of detritus such as dead fish, snails, etc. Typically, the water passes over biomedia. Biomedia having a large surface area is commonly available. A standard formula for conventional trickle filters is that biomedia having a volume equal to about 10% of the total volume in the tank must be used in the trickle filter. For example, a trickle filter servicing a 55 gallon tank would need 5.5 gallon of biomedia. Commercial designs for trickle filters include a translucent or semi-translucent compartment for the biomedia. Therefore, owners can watch the water pass through the trickle filter. Most commercial designs for trickle filters use containers that tend to be short and fat in ratio. The water passing through the trickle filter tends to take the path of least resistance and "channels" through the biomedia in the trickle filter. This causes the water to miss entire areas of the biomedia, thereby reducing the overall efficiency of the filter.
An object of the present invention is to improve the efficiency of the nitrification process to reduce the amount of ammonia and nitrite present in a water supply.
Anther object of the present invention is to provide separate locations for the growth of heterotrophic bacteria colonies and for the growth of nitrifying bacteria colonies to provide an optimum environment for nitrifying bacteria to oxidize ammonia into nitrite and then into nitrate.
Yet another object of the present invention is to maintain saturated oxygen levels within a water supply while minimizing the amount of ammonia and nitrate in the water supply.
In the biological filtration system of the present invention, water is pumped from the water supply into a micron filter. The micron filter filters particles having a size larger than one micron (1/1000 of an inch) from the water. After passing through the micron filter, water proceeds to an array of filter canisters. Water passes through spray nozzles which spray the water into an inlet end of the canisters. The spray nozzles break up the water and mix it with air which is supplied to the inlet end of the canisters. Water hits biomedia stored in the array of canisters. Any commercially available biomedia or any other inert substance which has a large surface area on which bacteria can grow may be used in the canisters. Water passes over the biomedia and is further mixed with air. At the bottom of the canisters, the water is collected and passed through a tube back into the water supply.
The spray nozzles disperse the water over a larger area of the biomedia to reduce channeling as the water passes over the biomedia in the canisters. In addition, the air supply to the top of the canisters from the air pump increases the atmospheric pressure around the biomedia so that dissolved gases are forced into the water to the point of super-saturation. Because water passing through the biomedia is prefiltered to remove particles greater than one micron from the water, the filtration system of the present invention promotes substantially separate environments for the growth of heterotrophic bacteria colonies and nitrifying bacteria colonies. Heterotrophic bacteria are attracted to the food supply provided by the organic material trapped in the micron filter. Heterotrophic bacteria feeds on the organic detritus trapped in the micron filter. Nitrifying bacteria grow on the biomedia in the array of canisters. There is a negligible food supply for heterotrophic bacteria in the array of canisters. Therefore, the biological filtration system of the present invention provides an optimum environment for nitrifying bacteria colonies to grow by eliminating competition with heterotrophic bacteria that feed on organic detritus.
The present invention requires biomedia equal to only 1% to 3% of the total tank volume. Therefore, for a 55 gallon tank, the present invention requires only 1/2 to 11/2 gallons of biomedia. The canisters for holding the biomedia in the present invention are preferably completely opaque. Heterotrophic bacteria growth is partially light dependent. Therefore, the darkness inside the canisters further discourages competition between heterotrophic bacteria and nitrifying bacteria. The canisters are relatively tall and thin in ratio compared to commercially available trickle filters. This further reduces the likelihood that channeling will occur as water passes over the biomedia located in the canisters.
According to one aspect of the present invention, a biological filtration system is provided for filtering a water supply. The filtration system includes a micron filter having an input and an output, and means for supplying water from the water supply to the input of the micron filter. The filtration system also includes a canister filled with a biomedia material. The canister has an inlet end coupled to the output of the micron filter and an outlet end. The filtration system further includes means for injecting air into the inlet end of the canister, and means for returning water from the outlet end of the canister to the water supply.
In one embodiment of the invention, the means for supplying water from the water supply to the input of the micron filter comprises a canister filter. The canister filter filters the water and pumps the water from the water supply through the canister filter to the input of the micron filter.
According to another aspect of the present invention, a biological filtration system is provided for filtering a water supply. The filtration system includes an elongated canister having an opaque outer wall defining an interior region which contains biomedia material therein. The canister has an inlet end and an outlet end. The filtration system also includes means for supplying water from the water supply to the inlet end of the canister. The supplying means includes a spray nozzle located adjacent the inlet end of the canister for dispersing the water entering the inlet end of the canister so that water flows substantially evenly over the biomedia inside the canister. The filtration system further includes means for supplying air into the inlet end of the canister so that air mixes with the dispersed water from the spray nozzle, and means for returning water from the outlet end of the canister to the water supply.
In an illustrated embodiment, the canister has a generally cylindrical shape. The filtration system may include an array of canisters to increase the capacity of the filtration system.
According to yet another aspect of the invention, a biological filtration system is provided for filtering a water supply. The biological filtration system reduces the quantity of ammonia and nitrite in the water supply. The filtration system includes means for separating heterotrophic bacteria colonies from nitrifying bacteria colonies, and means for supplying water from the water supply to the separating means. The filtration system also includes a canister filled with a biomedia material for promoting growth of nitrifying bacteria. The canister has an inlet end coupled to the outlet of the separating means so that water from the separating means flows through the canister and an outlet end. The filtration system further includes means for injecting air into the inlet end of the canister to provide oxygen for promoting oxidation of ammonia and nitrite by the nitrifying bacteria growing on the biomedia in the canister. The filtration system still further includes means for returning water from the outlet end of the canister to the water supply.
In the illustrated embodiment, the separating means includes a micron filter having an input and an output. The micron filter traps detritus and heterotrophic bacteria entrained in the water inside the micron filter to promote growth of heterotrophic bacteria colonies inside the micron filter instead of in the canisters. The micron filter includes a removable micron filter cartridge so that the detritus and heterotrophic bacteria in the micron filter cartridge can be removed from the water supply, thereby reducing the content of heterotrophic bacteria in the water supply. Therefore, in the illustrated embodiment, the removable micron filter cartridge provides means for removing detritus from the water supply to reduce the quantity of ammonia in the water supply.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.